The invention relates to a method of making a tapered wedge for use in gripping a multi-ply rope or cable, particularly in the anchoring of tendons used as reinforcements in pre-stressed or post-stressed concrete building members or structures.
In anchoring concrete-reinforcing tendons, it is well known to use wedges in the form of conical sleeves which are received in conical bores and are divided circumferentially into a plurality of complementary parts surrounding an axial aperture for the rope or cable. Although this system can yield satisfactory results, some important problems arise when it is used with stranded elements, e.g. multi-ply tendons comprising 2, 3 or 7 wires, all these arrangements being equally well known in present-day practice.
In fact, the wedge assembly or gripper to be employed with a multi-wire tendon is required to possess an internal diameter corresponding to the external enveloping circumference of the various wires, and contact between the internal surface of the wedges and the wires takes place exclusively along a line corresponding to the most external generatrix of each one of the said wires. The radial load produced by the wedging of the gripper means is concentrated along the said lines and attains extremely high specific values which may even cause rupture of the wedges or of the wire itself.
An attempt has been made to remove this disadvantage by imparting to the internal surface of the wedge a shape more or less complementary to the outer surface of the multi-wire tendon assembly, but this has involved costly manufacturing processes, and the results have not been totally satisfactory.